Sleeves which surround the nozzle bodies of fuel injection nozzles, in particular gasoline direct injection valves or diesel direct injection valves, are already known. They have the task of surrounding the nozzle body in the form of a cooling jacket. They furthermore also act as fastening means for fixing the injection nozzle in the holding part, in particular in the cylinder head. For example, DE 19743103 A1 discloses a heat protection sleeve which is inserted into a stepped receiving bore of a cylinder head of an internal combustion engine and which circumferentially surrounds a discharge-side nozzle body of a fuel injection valve that is inserted into the receiving bore.
Heat protection sleeves are however used not only with injection nozzles for internal combustion engines but also in different injection systems in other sectors, for example in the chemical industry. The heat protection sleeve is normally composed of copper or NiRo and covers the injection nozzle at the nozzle dome so as to prevent introduction of heat. Furthermore, the heat protection sleeve encases the injection nozzles along the nozzle shank in order to transport the temperature along the sleeves away from the nozzle tip to a cooled region of the installation space, for example of the cylinder head. The heat protection sleeve is in some cases formed integrally with the water sleeve that separates the cooling ducts formed in the cylinder head from the injector installation space.
A disadvantage of the conventional designs is that they require a relatively large passage bore in the holding part because the passage bore has to accommodate not only the nozzle body but additionally also the heat protection sleeve that encases the nozzle body. The relatively large passage bore in turn results in a relatively large force that is exerted on the injection nozzle from the combustion chamber side by the combustion chamber pressure, because said force increases with the square of the diameter of the bore. To reduce the surface area exposed to the combustion chamber pressure, the injection nozzle may, at its tip, be formed with a bevel via which it lies against the holding part with the interposition of a sealing disk or the heat protection sleeve. This however has the disadvantage that the clamping force with which the injection nozzle is clamped into the holding part is introduced at a relatively small diameter, which leads to disadvantageously high local stresses and intense deformations of the injection nozzle and/or of the holding part.